INTRODUCTION ii 



2. Galls at Base of Shoots 



The base of a shoot alone is involved ; the upper part is 

 able to continue its growth beyond the gall. This group 

 includes the pineapple galls of the Spruce caused by 

 aphides (Plate X.), and the spongy growths on various 

 Bedstraws caused by the dipteron Perrisia galii (figured 

 in Chapter V.), also on cruciferous plants by Dasymma 

 sisymhrii. 



3. Rosette Galls 



Axis of the bud much stunted, covered with densely 

 crowded leaf structures, between which the insects live. 



(a) Developed in the Foliage Region 



These galls resemble a miniature rosette, double Rose, or 

 Cabbage. Well-known examples are the rosettes at the tops 

 of Willow twigs caused by the dipteron Rhabdophaga rosaria, 

 and those on Hawthorn twigs caused by an allied insect, 

 Perrisia crataegi. 



(b) Developed in the Floral Region 



Bunches, rosettes, and balls, take the place of flowers. 

 Very common instances are the whitish hairy gall at the 

 top of the shoot in the Germander Speedwell, resulting from 

 attack by the dipteron Perrisia veronicae (Plate VIII.), and 

 the tuft of crowded erect leaves at the tip of a shoot in the 

 Yew, caused by the presence of the larvae of the dipteron 

 Oligotrophus taxi. An uncommon but very distinctive gall 

 belonging to this section is the tassel-like growth caused 

 by the homopteron Livia juncorum in the heads of various 

 Rushes. 



FUNGUS GALLS 



I. On Part of the Foliage Leaves 



The curious galls known as " Alpine Rose-apples," 

 frequent on the Continent on leaves of Rhododendrons 



